Pre-filled syringes each being filled with a certain injection solution of a certain volume are used in many medical fields since they enable accurate administration of a certain injection solution in a certain volume without error. As the pre-filled syringes of this type, a so-called injection needle mounting pre-filled syringe, in which an injection needle is previously secured to a distal end of a syringe body (barrel) has been used in many medical fields.
For the injection needle mounting pre-filled syringe, a cap for protecting the injection needle is used. This cap (needle shield assembly) has a two layer structure including an outer layer portion (shield) made of a transparent resin, and an inner layer portion (sheath) having elasticity (see Patent Literature 1, for example). This cap has an inner layer portion entire formed on the entire inner surface of an outer layer portion.